Written paper having minutes on old plot (9)
I believe the answer is:
monograph
'written paper' is the definition.
(type of academic paper)
'minutes on old plot' is the wordplay.
'minutes' becomes 'm' (common abbreviation).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'plot' becomes 'graph' (graphing is a kind of plotting).
'm'+'on'+'o'+'graph'='MONOGRAPH'
'having' is the link.
(Other definitions for monograph that I've seen before include "Treatise on phonogram" , "Essay" , "Detailed written study" , "Written work" , "Treatise on single subject" .)